Bloomberg isn't inventing the term rainbomb. It is evocative, yes. I feel that sort of colorful language is appropriate for describing an extreme weather event that dumps 8+ inches of rain in less than a day. Rainbomb or microburst, they are apparently quite effective at destroying vital infrastructure. Either way, you can't in good faith condemn the exploitation of color language to describe a destructive and lethal event by pointing out that that destructive and lethal event has a benign name.